Wednesday, November 21, 2012

QEMU Copy On Write

qcow stands for "QEMU Copy On Write" and denotes a disk storage optimization strategy that delays allocation of storage until it is actually needed. QEMU is an emulator and virtual machine container, and it can use a variety of virtual disk images which are generally associated with specific guests operating systems.

Once
QEMU has been installed, it should be ready to run a guest OS from a
disc image. This image is a file that represents the data on a hard
disc. From the perspective of the guest OS, it actually is a hard disc,
and it can create its own filesystem on the virtual disc.
You can download a few guest OS images from the QEMU website, including a simple 8MB image of a Linux distro. To run it, download and unzip the image in a folder and run the QEMU command.

qemu linux-0.2.img

Replace linux-0.2.img with the name of your guest OS image
file. If it has a GUI and you want to use your mouse with it,
double-click on the window and QEMU will grab your mouse. To make QEMU
release your mouse again, hold down the Control and Alt keys
simultaneously, then let go - your mouse will be released back to X.
Aurélien Jarno of Debian has prepared a number of pre-packaged Debian
qemu images for several architectures, including ARM, Sparc, PowerPC,
x86_64, and i386. They can be found at http://people.debian.org/~aurel32/qemu/